Collection literals are a pointless extension of the pattern matching syntax added to get around the fact that there is no way to name a generic type in C# without specifying its type arguments.
It's yet another double down on object initializers instead of writing constructors and factories, and unlike using a factory you have to fully express the result type of the collection instead of having it inferred (they are "target typed", another feature that probably should not have been added).
There is a pattern matching aspect but I think the energy behind it is largely motivated by a desire to clean up syntax when working with data structure based APIs and DSLs.
I've read the proposal, design meeting notes, and GH conversations. Not seeing a compelling counter argument here.
There is a "roles" proposal and investigation team. This roles proposal is going to unlock so much potential it is bonkers.